Polyolefin films and, in particular, polypropylene films, find wide usage in the preparation of bags on so-called vertical form and fill equipment. On this equipment, a flat sheet of film is converted into a bag by first forming it into a tubular shape, sealing the longitudinal seam, creating a transverse seal, filling the thus formed bag, sealing it at the top, then cutting the filled bag from the continuous tube and allowing it to free fall into a shipping container. When this technique is carried out using heat seal closing means, it is necessary that the film release readily from the heat seal apparatus in order to free fall. Most films do not release readily after heat sealing without some impetus to do so. In the case of the form and fill apparatus, this impetus is provided by the weight of the package. Since a weight of 200 to 400 grams may be necessary to release the film from the hot sealing equipment, the use of the form and fill technique has been essentially foreclosed form use with lighter packages.
It is the object of this invention to provide improved heat seal coatings for polyolefin films which, in addition to good heat sealing properties, exhibit excellent jaw release properties. Another object of this invention is to provide polyolefin films which can be readily heat sealed for use in form and fill operations. Yet another object is to provide polyolefin films which can be used for packaging relatively small, lightweight volumes of items via the vertical form and fill technique.